One of the key components of a computer system is a place to store data. Typically computer systems employ a number of storage means to store data for use by a typical computer system. One of the places where a computer can store data is in a disk drive which is also called a direct access storage device.
A disk drive or direct access storage device includes several disks which look similar to 45 rpm records used on a record player or compact disks which are used in a CD player. The disks are stacked on a spindle, much like several 45 rpm records awaiting to be played. In a disk drive, however, the disks are mounted to the spindle and spaced apart so that the separate disks do not touch each other.
The surface of each disk is uniform in appearance. However, in actuality, each of the surfaces is divided into portions where data is stored. There are a number of tracks situated in concentric circles like rings on a tree. Compact disks have tracks as do the disks in a disk drive. The tracks in either the disk drive or the compact disk essentially replace the grooves in a 45 rpm record. Each track in a disk drive is further subdivided into a number of sectors which is essentially just one piece of the track.
Disks in a disk drive are made of a variety of materials. Most commonly, each of the disks used in rotating magnetic systems is made of a substrate of metal, ceramic, glass or plastic with a very thin magnetizable layer on either side of the substrate. Such a disk is used in magnetic, and magneto-optical storage. Storage of data on such a disk entails magnetizing portions of the disk in a pattern which represents the data. Other disks, such as those used in CD's, are plastic. Data, such as songs, is stored using a laser to place pits in the media. A laser is used to read the data from the disk.
As mentioned above, to store data on a disk used in a rotating magnetic system, the disk is magnetized. In order to magnetize the surface of a disk, a small ceramic block known as a slider which contains at least one magnetic transducer known as a read/write head is passed over the surface of the disk. Some ceramic blocks contain a separate read head and a separate write head. The separate read head can be a magnetoresistive head which is also known as an MR head. The ceramic block is flown at a height of approximately six millionths of an inch or less from the surface of the disk and is flown over the track as the transducing head is energized to various states causing the track below to be magnetized to represent the data to be stored. Some systems now also use near contact recording where the slider essentially rides on a layer of liquid lubricant which is on the surface of the disk. With near contact recording, the ceramic block passes even closer to the disk.
To retrieve data stored on a magnetic disk, the ceramic block or slider containing the transducing head is passed over the disk. The magnetized portions of the disk generate a signal in the transducer or read head. By looking at output from the transducer or read head, the data can be reconstructed and then used by the computer system.
Like a record, both sides of a disk are generally used to store data or other information necessary for the operation of the disk drive. Since the disks are held in a stack and are spaced apart from one another, both the top and the bottom surface of each disk in the stack of disks has its own slider and transducing head. This arrangement is comparable to having a stereo that could be ready to play both sides of a record at anytime. Each side would have a stylus which played the particular side of the record.
Disk drives also have something that compares to the tone arm of a stereo record player. The tone arm of a disk drive, termed an actuator arm, holds all the sliders and their associated transducing heads, one head for each surface of each disk supported in a structure that looks like a comb at one end. The structure is also commonly called an E block. A portion of metal, known as a suspension, connects the sliders to the E block. At the other end of the actuator is a coil which makes up a portion of an voice coil motor used to move the actuator. The entire assembly is commonly referred to as an actuator assembly.
Like a tone arm, the actuator arms rotate so that the transducers within the sliders, which are attached to the actuator arm can be moved to locations over various tracks on the disk. In this way, the transducing heads can be used to magnetize the surface of the disk in a pattern representing the data at one of several track locations or used to detect the magnetized pattern on one of the tracks of a disk. Actuators such as the ones described above are common to any type of disk drive whether its magnetic, magneto-optical or optical.
Disk drives, like all other electronic devices, are becoming smaller and smaller. These smaller drives are being used in portable laptop computers and notebook computers which are also very small. These smaller drives can be removed from these smaller computers. Some of these smaller drives have the dimensions of a thick plastic credit card and can literally be carried around in a person's shirt pocket. The dimensions of these drives as well as other parameters are set by an industry standard called the Personal Computer Memory Card Industry Association, also known as PCMCIA. Due to the removability and small size, these drives are more susceptible to being dropped. The PCMCIA standard includes a series of drop tests that must be passed.
PCMCIA standard handling specifications require that products (including disk drives) be able to withstand drops of 30 inches onto very hard vinyl clad cement floor surface. This drop converts a significant amount of potential energy into kinetic energy. Accordingly, due to the reduced size of the disk drive, the PCMCIA DASD is more delicate and may be more susceptible to damage upon impact. The abrupt stop upon impact converts the kinetic energy into very high deceleration forces which may exceed the forces which the PCMCIA DASD components may accommodate.
Passing the PCMCIA standard requires either increasing the sturdiness of the internal components, or reducing the deceleration forces during impact to a point below critical acceleration levels for the components of the DASD. Increasing the sturdiness of the internal components in is more or less thwarted by the fact that the size of the devices has been reduced such that maintaining significant strength within some components is no longer possible. The remaining approach is to provide shock protection.
Although there are many possible sources for impacts to a disk drive, there seem to be two sources of impact which are more likely. The use of the disk drives or DASD in laptop and notebook size computers suggests a high probability of DASD impacts as a result of the computer being dropped or mishandled. The impacts also can result from any rough handling of the disk drive itself after it has been removed or before it has been placed into the slot in the computer. One example might be when the disk drive has been removed from the computer and placed in a shirt pocket of the user. When the user bends over to pick something up, the disk drive could fall onto the floor. Another example would be dropping a disk drive out of an executive's brief case or even fumbling a disk drive on a plane when trying to change from one hard disk drive to another disk drive. The impacts that occur to the disk drive when not installed in a computer, as a general rule, will probably be more serious than the impacts that result while the drive is housed within the computer.
Two types of impacts to an uninstalled disk drive seem to be particularly devastating. The first is when the disk drive falls on a corner of the disk drive. The second is known as a flat drop when a disk drive falls squarely on the entire base or cover of the disk drive. Thus, what is needed is a disk drive designed such that it can withstand the shock test set froth in the PCMCIA standard and more particularly designed to withstand the shock of impact caused by a drop on the corner of the drive and by a flat drop onto one of the major surfaces of the drive.
Another need for disk drives is the ability to seal the juncture between the base and the cover of the drive. The environment inside the disk drive must be very clean as the transducer is typically flown within 2 to 3 microinches of the surface of the disk. At such low heights, a particle of smoke from a cigarette is a major obstacle which would cause what is known as a "head crash" and would also result in a loss of data on the surface of the disk. A loss of data is a major concern to manufacturers of disk drives as it is a major concern to customers or users of disk drives.
To prevent contamination, most manufacturers provide tight seals around the joints in the disk drive and provide a filter to remove large particles and organic contaminants from any incoming air. The tight seals prevent unfiltered incoming air from entering where the seals are located and require the incoming air to pass through the filtered opening in the disk drive. It is important to also provide a good seal that is not easily removed from an assembled disk drive. If the seal can be removed, then the possibility occurs where unfiltered air can enter the disk drive. Also, the seal should be compliant to not only provide for a good seal between the various parts of the disk drive but also to provide for some shock absorption between the base and the cover of the drive.
It would also enhance manufacturability if the shock absorption system and the seal or gasket was one unitary piece which could be laid down on the base in a top down assembly of the disk drive.
Since these small disk drives are so susceptible to shock loading or impact, either while installed in a computer or when outside of the computer, it would also be advantageous to have a way to detect when a drive has undergone a shock loading or impact event of a selected magnitude. This would be advantageous since a drive may still work after undergoing such a shock and a user could then copy the data on the disk to assure against data loss, before failure occurred. Furthermore, a user who was purchasing these small drives would know if the disk drive has undergone such an impact and could refuse the purchase. It is thought that these drives will be very inexpensive and readily available in computer stores. With a visible shock detector, a purchaser could be assured that the drive had not already undergone some sort of shock during shipment. The store purchasing the drives would also be assured that the shipment was good and that there would not be an inordinate amount of returns of the drives purchased for resale. If purchased via mail order, the purchaser could also check the drive to assure that the drive had not been mishandled during shipment. If it had it could be returned and the company selling the drive could collect the cost of the drive from the shipper.
Thus, what is needed is a shock absorbing system for a disk drive that can pass the tests set forth in the PCMCIA standard and which can withstand drops on the corner of the disk drive as well as flat drops which are substantially along an entire edge or along an entire flat surface on the disk drive. What is also needed is a seal or gasket that is integral with the shock absorber and which can be placed on the base or cover easily to enhance manufacturability of the disk drive. In addition, the gasket and bumper should be locked into place so that the seal is not broken or so that the bumper does not separate from the disk drive during a shock. This mitigates the problems which could arise from taking in unfiltered air and from subsequent shocks. Also, there is a need for a way to indicate when such a disk drive has undergone shock loading or an impact of a certain level. Preferably, the indicator should be clearly visible from the exterior of the drive.